The present invention relates primarily to a liquid enclosing type vibration isolating apparatus used for supporting a vibration generating body, such as a power unit of an automotive engine, while isolating vibration.
As a vibration isolating apparatus for supporting a vibration generating body, such as an automotive engine, so as not to transmit its vibration to a car body and others, there has been known a liquid enclosing type vibration isolating apparatus which is arranged so as to perform a vibration damping function and a vibration isolating function by a liquid flow effect between two liquid chambers and a vibration isolating effect of a vibration isolating base made of rubber elastic body. In the vibration isolating apparatus, a partitioning member and a diaphragm are disposed for partitioning an inner space of main body having the vibration isolating base to form upper and lower chambers whose walls are partially composed of the partitioning member and/or the diaphragm, so as to provide two liquid chambers which are charged with liquid as sealed and communicated by an orifice passage at an outer periphery of the partitioning member.
For example, JP-A-08014315 proposes a liquid enclosing type vibration isolating apparatus in which the orifice for communicating the chambers is formed separately from the partitioning member so as to simplify the shape of the partitioning member and reduce its weight and cost.
In FIG. 12, the proposed vibration isolating apparatus is shown. A vibration isolating base 103 is attached to an opening portion of a cylindrical fitting 101 having a bottom, in which an intermediate cylinder 112 is disposed via a cylindrical rubber elastic body 113. A partitioning member 105, formed of an inverted cup-like cylinder, is attached with a diaphragm 110 at its opening and have an air chamber 111 inside the cylinder. The partitioning member 105 is fitted into the intermediate cylinder 112. An upper liquid chamber 106, whose wall is partly composed of the vibration isolating base 103, communicates with a lower liquid chamber 107, whose wall is partly composed of the diaphragm, by an orifice passage 108 outside of the intermediate cylinder. Then, a cylindrical reinforcing fitting 102, which extends downward along the intermediate cylinder 112 so as to press the partitioning member 105, is attached to an outer periphery of a lower end of the vibration isolating base 103. A through hole which communicates from the upper liquid chamber 106 to the orifice passage 108 is provided through the reinforcing fitting 102 and the intermediate cylinder 112.
Whereas assembly of each component has to be conducted within a liquid bath to enclose liquid as sealed within the liquid enclosing type vibration isolating apparatus constructed as de scribed above, it is not easy to align and assemble each component within the liquid bath.
That is, the proposed vibration isolating apparatus has a problem in that since the through hole, which communicates the orifice passage 108 with the upper liquid chamber 106, is provided through both the intermediate cylinder 112 and the reinforcing fitting 102 of the vibration isolating base, the communication hole provided through the reinforcing fitting 102 must be accurately aligned with the through hole provided through the intermediate cylinder 112 in assembling each component within the liquid bath, thus requiring complicated jigs, leading to the increase of the cost and possible failure in the assembly.
In view of the aforementioned problems, it is an object of the present invention to provide a liquid enclosing type vibration isolating apparatus capable of reducing a number of assembling steps and the cost, by reducing a number of members which need to be aligned as much as possible, and by allowing such members to be pre-assembled within air so as to simplify the assembly within liquid.